3D printing or additive manufacturing (AM) refers to any of the various processes for printing a three-dimensional object. Primarily additive processes are used, in which successive layers of material are laid down under computer control. These objects can be of almost any shape or geometry, and are produced from a 3D model or other electronic data source. Different types of 3D printers were developed over the years, such as 3D FDM (Fused Deposition Modeling) extrusion printers. 3D FDM extrusion printers are mostly based on melting a filament, e.g. plastics or metals, in a printer head. The maximum melting temperature of such 3D printers is limited to around 250° C. due to the relative low melting materials used for the printer heads.
There is a wish to be able to print glass objects, such as optical elements, with a 3D printer which requires a working temperature of the printer head of at least 200-2200° C.
Publication CN103395973 discloses a glass high temperature melting molding sprayer based on a 3D printing technology. The glass high temperature melting molding sprayer comprises a sprayer and a glass rod conveyor installed at the rear end of the sprayer. The sprayer comprises a protective shell, a high temperature resistant heat insulating insulation material layer, a high temperature electric heating wire layer, and a high temperature resistant corundum melting cavity that are sequentially connected. The sprayer is divided into three sections by the high temperature electric heating wire layer according to heating temperature. The three sections are a preheating warming section, an expansion softening section and a melting section. Each section is provided with a temperature sensor.
In publication CN103395973 the printing head comprises a heat wire which is enclosed by an insulation material layer to direct the most of the energy towards the corundum melting cavity at the center of the printing head. Such construction is not very energy efficient, and an unwanted amount of energy will be needed to reach the required temperatures. Furthermore, the use of refractory ceramics, such as corundum, will limit the maximum temperature of the printing head and therefore the printing of glass with a high viscosity like quartz glass or other glass types. A further problem with the use of refractory ceramics, such as corundum, for a high temperature 3D glass printing is the limited thermo shock resistance of most available ceramics and the chemical attack by glass causing impurities/bubbles in the molten glass.